Examples of the above-described cutting insert for milling that includes minor cutting edges are cutting inserts disclosed in the following PTL 1 and PTL 2.
A cutting insert that is described in PTL 1 includes major cutting edges and minor cutting edges each of which continues to a corresponding one of the major cutting edges via a transition region, and each of the minor cutting edges is configured as a cutting edge that is curved in a convex manner when viewed from the side in a direction perpendicular to a flank face.
A cutting insert that is described in PTL 2 includes auxiliary cutting edges (minor cutting edges) each having a protruding shape that is oblique to a reference plane parallel to a top surface. Corner transition parts (so-called noses R) are present on opposite sides of each of the auxiliary cutting edges. One of the corner transition parts (hereinafter referred to as a portion A) connects the auxiliary cutting edge and a corresponding one of non-chip-removing cutting edges having the largest height to each other, and the other one of the corner transition parts (hereinafter referred to as a portion B) connects the auxiliary cutting edge and a corresponding one of main cutting edges having a small height to each other.
In this configuration, the other one of the corner transition parts (the portion B) is capable of smoothly connecting the auxiliary cutting edge and the corresponding main cutting edge to each other by being formed as a cutting edge having a protruding shape when viewed from the side; however, the one of the corner transition parts (the portion A) cannot maintain a protruding shape because the difference in the heights of the auxiliary cutting edge and the corresponding non-chip-removing cutting edge needs to be accommodated, and thus, there is a difference in level between the non-chip-removing cutting edge and the auxiliary cutting edge.